Circular RNAs (circRNAs) are RNA molecules with closed ring structure and are widely distributed in various tissues. circRNAs are more stable than linear RNAs. They can be divided into three categories: exonic circular RNA, exon-intron circular RNA, and circular intronic RNA. The main functions of circRNAs are acting as a sponge of microRNAs, binding to RNA binding proteins, affecting the formation of homologous linear mRNAs and regulating transcription. Besides, the latest research found that some circRNAs can directly code protein, which changed the impression that circRNAs only act as noncoding RNAs. This may provide a new idea for future studies of circRNAs. In recent years, a large number of studies have shown that the abnormal expression of circRNAs plays an important role in the occurrence and development of gastric cancer. The expression of circRNAs in tissues, plasma and exosomes is variable between healthy individuals and patients with gastric cancer. Some gastric cancer-associated circRNAs are more sensitive and more specific than traditional gastric cancer markers. For example, hsa_circ_0065149 level is significantly decreased in exosome of gastric cancer patient, while the levels of circPTPN22, hsa_circ_0004771, and hsa_circ_0141633 in the plasma of gastric cancer patients are increased, indicating the potential of circRNAs as novel diagnostic markers for gastric cancer. Studies on gastric cancer-associated drug resistance have found that some circRNAs including circ-PVT1, circCUL2, hsa_circ_0001313, hsa_circ_0110805, and circVAPA affect the chemoresistance of gastric cancer cells through the circRNA/miRNA/mRNA arises. The main functions of circRNAs are by acting as microRNA sponge to regulate the expression of targeted mRNAs, functioning as tumor promoter or suppressor, thereby affecting gastric cancer proliferation, differentiation and metastasis. The aberrant expression of circRNAs plays a crucial role in gastric carcinogenesis. For example, circRBM33, one of the gastric cancer-associated upregulated circRNAs, upregulates the expression of interleukin-6 (IL-6) through miR-149/IL-6 axis, which in turn promotes gastric cancer proliferation. Hsa_circ_002059 inhibits gastric cancer proliferation and migration by inhibiting the expression of miR-182 and inducing the expression of Metastasis suppressor 1 (MTSS1). In addition, hsa_circ_0005529, circRanGAP1, circPIP5K1A, circMAT2B, and circMTO1 may be promising as novel targets for the treatment of gastric cancer. The results of studies on gastric cancer-related circRNAs are helpful for us to understand the mechanism underlying gastric cancer occurrence and provide basics for the diagnosis and treatment of gastric cancer.